MAMMALS

All mammals are endothermic (warm-blooded), have some fur
or hair on their body, and feed their young milk. They have a bony skeleton
with a backbone, and their lower jaw, made of one bone, hinges directly onto
the skull. Mammals breathe using lungs. A few mammals lay eggs, and some carry
their young in pouches, but most have a placenta and give birth to live young.
Mammals are found all over the world, on land, in the air, and in water.

The brown bear is an omnivore, eating plants and animals. It walks
on all fours, with its heel on the ground. It is a placental mammal, which
means that the young are able to develop and grow inside the female’s
body. The cubs look like tiny adults when born, but are helpless and stay with
their mother for at least two years.

Bats are the only mammals that fly. A bird’s wing is made up
of the whole of the forelimb, but in bats the flight membrane stretches between
its very long fingers. Most bats feed at night and rest, often in large groups,
during the day.

CLASS: MAMMALIA

There are about 4,500 species of mammal in a total of 21 orders, of
which the following are a selection.

Class: Monotremata

(duck-billed
platypus, echidna)

Features: lay eggs, short legs, small
head, tiny eyes

Class: Diprotodonta

(pouched
mammals)

Features: young born at early stage and
cared for in pouch

Class: Perissodactyla

(odd-toed, hoofed
mammals)

Features: leg’s weight on central
toe

Class: Carnivora

(flesh-eating
mammals)

Features: carnassial (sharp, cheek)
teeth for cutting flesh

Class: Cetacea

(whales, dolphins,
porpoises)

Features: move tail up and down to
swim

Class: Primates

(lemurs, apes, monkeys,
humans)

Features: large brain, forward-facing
eyes

Class: Rodentia

(rodents)

Features: incisor teeth grow
continuously, most have good sense of smell and hearing

DIVING PLATYPUS

The duck-billed platypus closes its eyes, ears, and nose when diving
and finds its way using sense receptors around its bill. The platypus lays
eggs. It does not have nipples, so when the young hatch, they suck milk from
the fur around the openings of the milk glands. It lives by rivers in Australia
and Tasmania.

LEAPING DOLPHIN

Dolphins, like whales, spend their entire life in the water, but
must still surface to breathe air through their lungs. Their fat reserves,
called blubber, keep them warm in cold seas.